I have a 98 ti with factory cruise. It has worked fine for the first 150k mi. Now if I set it on a cold day (less than 30 deg F) it has the bad habit of kicking off. It will stay on for a few seconds, then kick off. It will re-engage (If I push the level) and kick off again. Then after I've been on the road for a while (10 min.) it will stay on. This never happens when it's warm, and is way worse when it's colder (less than 20 deg F). Any thoughts?

Mine does the same thing. Not really sure, but just wanted to let you know you are not alone. I always assumed that it was due to load on the motor or something related to the temp and motor temp. i dunno.

do you have a 5sp or auto? mine is 5sp, so maybe related to type of trans too.

yeah, i assume it has to do with temp of something (like temp of motor, how it runs do to temp, the cat, the trans) no, no lights flash. if you set it, it might stay set for anywhere from 2 seconds to 5 seconds. should not be load, since it will do it even if you are going down a hill and at any speed. sometimes if you continue to set it, it will stop kicking off and work fine.

i never use it much except for long trips, but my car is normally warm enough and will not kick off by then.

Thanks for the replies. Especially the one that confirmed I'm not alone. It is a 5 speed. I've had the car for 4 yrs from 70,000 to now at 164,000. I added an OBC to it, but there is no connection between the cruise and the OBC (except for the serial link, but I doubt they use that for actual vehicle control functions.)

I've had the mechanical cruise unit apart, and everything looks perfect in there. My theory is that it has to do with the temperature of the electric motor it's self. That is, that the bearings in it bind up when it's cold and as it warms the motor has less internal drag. It's warm now and it works first time every time!

I have heard of several instances where people comment that their cruise control on BMW's does not work in temps. below 35*-40*. My take is that this IS, in fact, a safety feature that is probably also somehow connect to the chime you hear when outside temps get near the freezing point.

If you hit a patch of black ice, you definitely do NOT want your cruise control engaged- BMW engineers are probably just ensuring that you cannot engage the cruise control in freezing temps, when a driver probably should be paying a little more direct attention to things like throttle and braking.

I am skeptical of the cold temp/safety business. I have an E28 that had an intermittent CC, possibly due to a circuit board solder problem. The easiest/cheapest solution was to replace the CC brain/box.

It's not a safety feature. The extreme temperature puts stress on an instable electrical component somewhere in your system. Could be a speed sensor, could be the actuator, could be the ground, could be the harness. Need to do some looking around and diagnosing.